Calculation method and coating composition manufacturing method

Abstract

This calculation method includes a step for converting a tristimulus-value direct reading method into a spectral colorimetric method, and is used in computer color matching using a computer.

Description

Calculation method and method for producing coating composition

[0001] The present invention relates to a calculation method (particularly a method for calculating spectral reflectance) and a method for producing a coating composition.

[0002] Paint manufacturers mix paint compositions to achieve a target paint color. Customers who use these colorimeters manage their paint compositions based on the color difference measured with a colorimeter. Colorimeters can be broadly classified into two types: direct-reading tristimulus colorimeters, which directly measure the three stimulus values ​​that form the basis of color, and spectrophotometers, which measure spectral reflectance (transmittance) and then calculate the tristimulus values. Both paint manufacturers and customers use either of these types of devices.

[0003] It is well known that different color difference meters will result in different color difference values. In recent years, with the demand for precision in color matching increasing, the difference in color difference values ​​due to different color difference meters is usually not negligible. For this reason, paint manufacturers use color difference meters specified by their customers to match colors.

[0004] Here, computer color matching (CCM) using a computer is known as a color matching method used by paint manufacturers (for example, Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2007-314772

[0006] Computer color matching is a calculation performed using spectral reflectance data that indicates the relationship between wavelength and spectral reflectance. Spectroscopic colorimeters measure color differences from the spectral reflectance of each wavelength when measuring color differences, so measuring color differences can provide the spectral reflectance data used for computer color matching. However, tristimulus value direct-reading colorimeters do not obtain spectral reflectance data when measuring color differences.

[0007] For this reason, when managing the color difference of a paint composition using a stimulus value direct reading colorimeter (for example, by a paint manufacturer to suit a customer), there is a problem that computer color matching cannot be performed because spectral reflectance data is not obtained.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a calculation method and a paint manufacturing method that are capable of performing computer color matching regardless of the type of color measurement device.

[0009] The present invention has the following essential features: (1) A calculation method, which includes a step of converting a tristimulus value direct reading method into a spectrophotometric colorimetric method, and is used for computer color matching using a computer.

[0010] (2) a first acquisition step using a spectrophotometric colorimeter to acquire first spectral reflectance data of a first coating film obtained from a coating composition comprising primary color colorants, the first spectral reflectance data being data showing the relationship between wavelength and spectral reflectance; a second acquisition step using a tristimulus value direct reading colorimeter to acquire color values ​​of each primary color colorant of the color of a second coating film obtained from a coating composition comprising primary color colorants; and a first calculation step using the first spectrophotometric colorimeter acquired in the first acquisition step to calculate a provisional blend of primary color colorants such that the color values ​​measured using the spectrophotometric colorimeter correspond to the color values ​​acquired in the second acquisition step. a second calculation step in which a second calculation unit uses the first spectral reflectance data acquired in the first acquisition step to calculate second spectral reflectance data for each primary colorant of the color of the coating film obtained using the temporary blend, wherein the second spectral reflectance data is data that indicates the relationship between wavelength and spectral reflectance.

[0011] (3) The method for calculating a spectral reflectance according to (2), further comprising a coefficient calculation step of calculating an absorption coefficient K and a scattering coefficient S of each primary color colorant based on the first spectral reflectance data acquired in the first acquisition step, wherein in the first calculation step, a provisional blend of the primary color colorants is calculated using the absorption coefficient K and the scattering coefficient S calculated in the coefficient calculation step.

[0012] (4) The method for calculating a spectral reflectance according to (3), wherein the second calculation step includes: a coefficient ratio calculation step of calculating a coefficient ratio K / S corresponding to the provisional blend based on the provisional blend calculated in the first calculation step and the absorption coefficient K and the scattering coefficient S of each primary color colorant calculated in the coefficient calculation step; and a second spectral reflectance data calculation step of calculating the second spectral reflectance data from the calculated coefficient ratio K / S.

[0013] (5) The method for calculating a spectral reflectance according to any one of (2) to (4), wherein the first calculation step is performed using a mathematical optimization method or a brute force search method.

[0014] (6) The method for calculating a spectral reflectance according to any one of (2) to (5), wherein the first coating film and the second coating film are the same coating film.

[0015] (7) The method for calculating a spectral reflectance according to any one of (2) to (5), wherein the first coating film and the second coating film are different coating films, and a color difference ΔE between the first coating film and the second coating film is 2 or less.

[0016] (8) The method for calculating a spectral reflectance according to any one of (2) to (7), wherein the number of types of the first coating film is 10 or more.

[0017] (9) A method for producing a coating composition, which involves calculating a formulation suitable for obtaining a coating composition having desired coating properties by computer color matching using a computer, and obtaining the coating composition using the calculated formulation, the method comprising: a first acquisition step using a spectral colorimeter to acquire first spectral reflectance data of a first coating film obtained from a coating composition comprising primary colorants, the first spectral reflectance data being data showing the relationship between wavelength and spectral reflectance; a second acquisition step using a tristimulus value direct reading colorimeter to acquire color values ​​of each primary colorant of the color of a second coating film obtained from a coating composition comprising the primary colorants; and a first calculation step using the first spectral reflectance data acquired in the first acquisition step to calculate a tentative formulation of primary color colorants such that the color values ​​measured using the spectral colorimeter correspond to the color values ​​acquired in the second acquisition step. a second calculation step in which a second calculation unit calculates second spectral reflectance data of each primary color colorant of the color of the paint film obtained using the temporary blend using the first spectral reflectance data acquired in the first acquisition step, the second spectral reflectance data being data that indicates the relationship between wavelength and spectral reflectance; and wherein the second spectral reflectance data calculated in the second calculation step is used in the computer color matching.

[0018] According to the present invention, it is possible to provide a calculation method and a paint manufacturing method that can perform computer color matching regardless of the type of color measurement device.

[0019] FIG. 1 is a flow diagram of a method for calculating spectral reflectance according to one embodiment of the present invention. FIG. 2 is a diagram for explaining colorimetry in the case of a spectral colorimetric device. FIG. 3 is a diagram showing an example of first spectral reflectance data (upper diagram) and an example of color values ​​calculated based on the first spectral reflectance data (lower diagram). FIG. 4 is a diagram for explaining colorimetry in the case of a tristimulus value direct reading colorimetric device. FIG. 5 is a diagram for explaining calculation of a provisional blend of primary color colorants. FIG. 6 is a diagram for explaining a method for calculating spectral reflectance according to one embodiment of the present invention.

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] <Calculation Method> A calculation method according to one embodiment of the present invention includes a step of converting tristimulus value direct reading data into spectrophotometric colorimetry, and is used for computer color matching using a computer. According to the calculation method of this embodiment, even when management is performed using tristimulus value direct reading data, the data can be converted into spectrophotometric colorimetry data to obtain spectral reflectance data, making it possible to perform computer color matching.

[0022] The tristimulus value direct reading method can be one that uses a tristimulus value direct reading color measuring device, and the spectrophotometric colorimetric method can be one that uses spectrophotometric colorimetric method.

[0023] <Method for Calculating Spectral Reflectance> Next, a method for calculating spectral reflectance according to one embodiment of the present invention will be described by way of example. Fig. 1 is a flow chart of a method for calculating spectral reflectance according to one embodiment of the present invention.

[0024] As shown in FIG. 1 , in the method for calculating spectral reflectance according to this embodiment, first, first spectral reflectance data of a first coating film obtained from a paint composition containing primary colorants is acquired using a spectral colorimeter (first acquisition step: S101). FIG. 2 is a diagram illustrating colorimetry using a spectral colorimeter. FIG. 2 illustrates a painted panel having three first coating films (see the left diagram in FIG. 2 ) each obtained from a paint composition containing three primary colorants (black colorant, yellow colorant, and blue colorant, from the top). Colorimetry using a spectral colorimeter (see the center diagram in FIG. 2 ) can provide first spectral reflectance data (see the right diagram in FIG. 2 ), which is data showing the relationship between wavelength and spectral reflectance. Such first spectral reflectance data is acquired for each primary colorant. FIG. 3 (top diagram) shows an example of the first spectral reflectance data. As also illustrated in FIG. 3, the first spectral reflectance data may be data consisting of one type of primary colorant, or may be data consisting of a primary colorant mixed with a white colorant or a black colorant.

[0025] Next, a tristimulus value direct-reading colorimeter is used to obtain the color values ​​of each primary colorant of the color of the second coating film obtained from a coating composition containing the primary colorants (second obtaining step: S102). Figure 4 is a diagram for explaining colorimetry using a tristimulus value direct-reading colorimeter. Figure 4 illustrates a painted panel having a second coating film (see the left diagram in Figure 4) obtained from a coating composition containing one primary colorant (green colorant). Colorimetry using a tristimulus value direct-reading colorimeter (see the center diagram in Figure 4) does not provide spectral reflectance data (see the right diagram in Figure 4).

[0026] Here, it is preferable that the first coating film (used in the first obtaining step) and the second coating film (used in the second obtaining step) are the same coating film, because this can improve the reproducibility of the spectral reflectance.

[0027] Alternatively, it is also preferable that the first coating film and the second coating film are different coating films, and the color difference ΔE between the first coating film and the second coating film is not more than 2. This is because by using coating films that are as similar in color as possible, the accuracy of the calculation of the provisional blend, which will be described later, can be improved.

[0028] It is also preferable that the number of types of first coating films is 10 or more, because this can improve the accuracy of calculation of the provisional blend, which will be described later.

[0029] Next, a first calculation unit uses the first spectral reflectance data acquired in the first acquisition step (S101) to calculate a provisional blend of primary colorants such that the color values ​​measured using the spectrophotometer correspond to the color values ​​acquired in the second acquisition step (first calculation step: S103). The first calculation unit can be any known computer or the like.

[0030] As shown in FIG. 3, by acquiring the first spectral reflectance data, a color value (e.g., L ＊ a ＊ b ＊It is possible to calculate the absorption coefficient K and scattering coefficient S of each primary color colorant based on the first spectral reflectance data acquired in the first acquisition step (S101). More specifically, it is preferable to further include a coefficient calculation step, prior to the first calculation step (S103), after the first acquisition step (S101), in which the absorption coefficient K and scattering coefficient S of each primary color colorant are calculated based on the first spectral reflectance data acquired in the first acquisition step (S101). This makes it possible to perform the calculations described above. The coefficient calculation step may be performed before or after the second acquisition step (S102). The coefficient calculation step can be performed, for example, by calculations based on the Kubelka-Munk theory.

[0031] 5 is a diagram illustrating the calculation of a provisional mixture of primary colorants. In the first calculation step (S103), a provisional mixture of primary colorants corresponding to the color value (of the green colorant) acquired in the second acquisition step (S102) is calculated based on the first spectral reflectance data in the case of a spectral colorimetric device. That is, in this example, based on the first spectral reflectance data in the case of a spectral colorimetric device (see FIG. 3), the provisional mixture corresponding to the color value of the green colorant in a tristimulus value direct-reading colorimetric device is calculated to be 7% black colorant, 55% yellow colorant, and 38% blue colorant (see FIG. 5, in which the mixture amounts (colorant mixture ratios) of each color are schematically indicated by the vertical width of each color).

[0032] As a specific calculation, in the first calculation step (S103), it is preferable to calculate a provisional blend of the primary color colorants using the absorption coefficient K and the scattering coefficient S calculated in the coefficient calculation step. This calculation can be performed using a mathematical optimization method, although it is not particularly limited.

[0033] In addition, it is preferable that the first calculation step (S103) is performed using a mathematical optimization method or a brute force search method.

[0034] Next, a second calculation unit uses the first spectral reflectance data acquired in the first acquisition step (S101) to calculate second spectral reflectance data for each primary colorant of the coating film color obtained using the temporary blend (second calculation step: S104). The second spectral reflectance data is also data indicating the relationship between wavelength and spectral reflectance. The second calculation unit can be any known computer or the like.

[0035] That is, since the provisional blend calculated in the first calculation step (S103) is for the case of a spectral colorimetric device, by using the first spectral reflectance data acquired in the first acquisition step (S101) (in this example, by using the first spectral reflectance data of the black colorant, yellow colorant, and blue colorant that make up the provisional blend), it is possible to calculate second spectral reflectance data of each primary colorant of the color of the coating film obtained using the provisional blend (in this example, the green colorant obtained by provisionally blending the black colorant, yellow colorant, and blue colorant) (see the right diagram in Figure 5).

[0036] The second spectral reflectance data thus obtained can be regarded as the spectral reflectance data of each primary colorant measured using a tristimulus value direct-reading colorimeter. This makes it possible to calculate the blending and color of a coating film obtained from a coating composition containing each primary colorant when using a tristimulus value direct-reading colorimeter, for example.

[0037] As a specific calculation, it is preferable that the second calculation step (S104) includes a coefficient ratio calculation step of calculating a coefficient ratio K / S corresponding to the provisional blend based on the provisional blend calculated in the first calculation step (S103) and the absorption coefficient K and scattering coefficient S of each primary color colorant calculated in the coefficient calculation step, and a second spectral reflectance data calculation step of calculating second spectral reflectance data from the calculated coefficient ratio K / S.

[0038] The coefficient ratio calculation step can be performed by calculation using, for example, Duncan's color mixing theory, and the second spectral reflectance data calculation step can be performed by calculation using, for example, Kubelka-Munk theory.

[0039] As described above, according to the method for calculating spectral reflectance of the present embodiment, even when management is performed using the tristimulus value direct reading method, spectral reflectance data (second spectral reflectance data) using the tristimulus value direct reading method can be calculated, and this spectral reflectance data can be regarded as the spectral reflectance data of each primary color colorant measured using a tristimulus value direct reading colorimetric device. Therefore, by using this spectral reflectance data, computer color matching can be performed regardless of the type of colorimetric device.

[0040] FIG. 6 is a diagram illustrating a method for calculating spectral reflectance according to one embodiment of the present invention. In the example of FIG. 6, color values ​​for the second coating film are obtained not only using a tristimulus value direct-reading colorimeter, but also using a spectral colorimeter. This can be performed before the first calculation step. Then, when calculating a provisional blend in the first calculation step, a provisional blend is created by adding a black colorant and / or a white colorant (only) to a primary colorant (in this example, a green colorant) corresponding to the color values ​​obtained by the spectral colorimeter. In this example, the blend is 1% black colorant, 1% white colorant, and 98% green colorant. This method allows for more reliable reproducibility of color values ​​using the tristimulus value direct-reading colorimeter based on the provisional blend in the case of a spectral colorimeter, thereby enabling more accurate second spectral reflectance data to be obtained. This can also improve the accuracy of computer color matching.

[0041] <Method for producing a coating composition> Next, an example of a method for producing a coating composition according to one embodiment of the present invention will be described. The method for producing a coating composition according to one embodiment of the present invention is a method for producing a coating composition in which a formulation suitable for obtaining a coating composition having desired coating properties is calculated by computer color matching using a computer, and a coating is obtained using the calculated formulation.

[0042] In the method for producing a coating composition of this embodiment, first, a spectrophotometer is used to obtain first spectral reflectance data of a first coating film obtained from a coating composition containing primary colorants. This step is similar to the "first obtaining step" in the embodiment of the method for calculating spectral reflectance, and therefore will not be described again.

[0043] Next, a tristimulus value direct-reading colorimeter is used to obtain the color values ​​of each primary colorant of the color of the second coating film obtained from the coating composition containing the primary colorants. This step is similar to the "second obtaining step" in the embodiment of the method for calculating spectral reflectance, and therefore will not be described again.

[0044] Next, a first calculation unit uses the first spectral reflectance data acquired in the first acquisition step to calculate a provisional blend of primary colorants such that the color values ​​measured using the spectral colorimeter correspond to the color values ​​acquired in the second acquisition step. This step is similar to the "first calculation step" in the embodiment of the method for calculating spectral reflectance, and therefore will not be described again.

[0045] Next, a second calculation unit calculates second spectral reflectance data for each primary colorant of the color of the coating film obtained using the temporary blend, using the first spectral reflectance data acquired in the first acquisition step. This step is similar to the "second calculation step" in the embodiment of the method for calculating spectral reflectance, and therefore will not be described again.

[0046] Next, in computer color matching, the second spectral reflectance data calculated in the second calculation step is used. According to the method for producing a coating composition of this embodiment, as explained in the embodiment of the method for calculating spectral reflectance, even when management is performed using a tristimulus value direct reading method, spectral reflectance data (second spectral reflectance data) using the tristimulus value direct reading method can be calculated and the spectral reflectance data can be regarded as the spectral reflectance data of each primary color colorant measured using a tristimulus value direct reading colorimeter, and by using the spectral reflectance data, computer color matching can be performed regardless of the type of colorimeter.

[0047] In this specification, color values ​​are, for example, L ＊ a ＊ b ＊ L in color space ＊ Value, a ＊ value, b ＊ value (JIS Z8781-4 (2013)), X-Y-Z color system, R-G-B color system, Yxy color system, Hunter L-a-b color system, L ＊ -C ＊ -h ＊The color value can be measured using a known color measurement method, and as an example, the L value can be measured by using a CM-512m3 commercially available from Konica Minolta, Inc., by irradiating a light source at angles of 25°, 45°, and 75°, assuming that the light receiving part perpendicular to the coating film is at 0°. ＊ Value, a ＊ value, b ＊ The value can be measured. Alternatively, the measurement can be performed using an X-Rite MA68II (manufactured by X-Rite). The measurement angle can be adjusted appropriately depending on the purpose or the equipment used. Any other index can be used. Furthermore, for example, any index can be used, such as reflection spectrum data, which is an index in which the reflection spectrum intensity is expressed as a color in 5 nm increments from 380 nm to 780 nm.

[0048] In another aspect, the first calculation step (S103) may involve adding a correction function instead of calculating a provisional blend of primary colors. That is, in another aspect, in the first calculation step, a first calculation unit uses the first spectral reflectance data acquired in the first acquisition step to calculate a correction function to the first spectral reflectance data so that the color values ​​measured using the spectral colorimeter correspond to the color values ​​acquired in the second acquisition step. That is, the correction function is a function that indicates the difference between the second spectral reflectance data and the first spectral reflectance data, and adding the correction function to the first spectral reflectance data results in the second spectral reflectance data. And in another aspect, the second calculation step is a step in which a second calculation unit uses the first spectral reflectance data acquired in the first acquisition step to calculate second spectral reflectance data for each primary color of the coating film color obtained using the correction function, and the second spectral reflectance data is data that indicates the relationship between wavelength and spectral reflectance.

[0049] [(A) Preparation] First, a method for preparing the colorants used in the examples will be described. <(a1) Preparation Example of White Colorant> 55 parts by mass of polyester resin (A) as the resin, 12 parts by mass of Super Beckamine L-155-70 as the crosslinking agent, 8 parts by mass of T-SOL 150 as organic solvent 1, 7 parts by mass of cyclohexanone as organic solvent 2, and 18 parts by mass of Typeque CR-97 as the white pigment were mixed, and the mixture was dispersed using a sand mill (dispersion medium: glass beads) until the maximum particle size of the pigment coarse particles was 10 μm or less, thereby preparing a white colorant.

[0050] <(a2) Preparation Examples of Other Colorants> Black colorants and green colorants were prepared in the same manner as in the preparation example of the white colorant, except that the types and amounts of each material were changed as shown in Table 1. The formulations of each colorant are shown in Table 1.

[0051]

[0052] <(a3) Method for preparing coating film> <Preparation example of calculation coating composition W> 100 parts by mass of the white colorant and 3 parts by mass of Disparlon OX-70 as a surface conditioner were added and mixed uniformly using a disper to prepare calculation coating composition W.

[0053] <Preparation Examples of Other Calculation Coating Compositions> Calculation coating compositions K and G, and calculation mixed coating compositions W-K and WG were obtained by preparation in the same manner as in the preparation example for calculation coating composition W, except that the type and amount of each material was changed as shown in Table 2 below. The formulations of each calculation coating composition are shown in Table 2.

[0054]

[0055] Preparation of Polyester Resin (A): 155 parts by weight of neopentyl glycol, 222 parts by weight of 1,6-hexanediol, 50 parts by weight of trimethylolpropane, 441 parts by weight of isophthalic acid, 132 parts by weight of adipic acid, and 26 parts by weight of xylene were mixed in a reaction vessel equipped with a thermometer, a condenser, and an agitator, and the mixture was gradually heated to 230°C in a nitrogen stream. The resulting water was distilled off, and an esterification reaction was carried out until the amount of dehydration reached 126 parts by weight and the reaction mixture reached a predetermined viscosity. The temperature of the reaction vessel was then lowered to 50°C, and 90 parts by weight of xylene, 379 parts by weight of T-SOL 150, and 87 parts by weight of propylene glycol monomethyl ether acetate were mixed to prepare a coating film-forming resin (A) (polyester resin; solids concentration: 60% by weight, number average molecular weight: 3,000, hydroxyl value: 55 mgKOH / g).

[0056] Details of the materials used in preparing the coating composition are as follows: Crosslinker: Super Beckamine L-155-70 (DIC Corporation), butylated melamine resin; solid content: 70% by mass Surface conditioner: Disparlon OX-70 (Kusumoto Chemicals Co., Ltd.), acrylic surface conditioner; solid content: 30% by mass White pigment: Typec CR-97 (Ishihara Sangyo Kaisha), titanium dioxide Black pigment: Black 6350 (Asahi Chemical Industries Co., Ltd.), chromium iron oxide Green pigment: Lionol Green 6YKP-N (Toyocolor Co., Ltd.), brominated copper phthalocyanine Yellow pigment: TAROX synthetic iron oxide HY-100 (Titanium Kogyo Co., Ltd.), yellow iron oxide Red pigment: TODA COLOR KN-V (Toda Pigment Co., Ltd.), ferric oxide Organic solvent 1: T-SOL 150 (manufactured by JXTG Nippon Oil & Energy Corporation), an aromatic solvent. Organic solvent 2: cyclohexanone (manufactured by Shoei Chemical Industry Co., Ltd.), a ketone solvent.

[0057] <Method of preparing calculation coating film W> Fine Tough G Primer (epoxy resin primer: manufactured by Nippon Paint Industrial Coatings Co., Ltd.) was applied as a primer coating to the surface of a substrate (zinc-aluminum alloy plated steel sheet: 1,800 x 300 x 0.35 mm) using a roll coater (standard film thickness: 5 μm), and then baked for 60 seconds under conditions that the maximum temperature reached by the material was 210°C, forming a primer coating film. Next, calculation coating composition W was applied to the primer coating using a roll coater (standard film thickness: 15 μm), and then baked for 60 seconds under conditions that the maximum temperature reached by the material was 250°C, and then immediately cooled, thereby obtaining a coating film of calculation coating composition W (calculation coating film W).

[0058] In the same manner as in the preparation of the calculation coating film W, calculation coating films K, G, Y, R, and B, and calculation mixed coating films WK, WG, WY, WR, and WB were obtained.

[0059] <Acquisition Step> [[(B) First Acquisition Step]] The first spectral reflectance data of the first coating film obtained in the first acquisition step was measured by the following method.

[0060] Measurement of Spectral Reflectance Data The relationship between wavelength and spectral reflectance was determined for the various calculation coating films (W, K, G, Y, R, B, W-K, W-G, W-Y, W-R, W-B) obtained above using a spectral colorimeter SE7700 (manufactured by Nippon Denshoku Industries Co., Ltd.), which is a spectral colorimeter.

[0061] [(C) Second Obtaining Step] The color value of the second coating film obtained in the second obtaining step was measured by the following method.

[0062] Measurement of color values ​​The color (L) of the various coatings for calculation (W, K, G, Y, R, B, W-K, W-G, W-Y, W-R, W-B) obtained above was measured using a color meter SM-T (manufactured by Suga Test Instruments Co., Ltd.), which is a tristimulus value direct reading color measuring device. ＊ , a ＊ , b ＊ value) was measured.

[0063] [(D) Coefficient Calculation Step] From the relationship between wavelength and spectral reflectance of calculation coating film W obtained above, the absorption coefficient K and scattering coefficient S of calculation coating film W were each calculated. From the relationship between wavelength and spectral reflectance of calculation coating films W, K, and W-K obtained above, the absorption coefficient K and scattering coefficient S of calculation coating film K were each calculated. Similarly, from the relationship between spectral reflectance of calculation coating films W, G, and W-G obtained above, the absorption coefficient K and scattering coefficient S of calculation coating film G were each calculated. Similarly, from the relationship between spectral reflectance of calculation coating films W, Y, and W-Y obtained above, the absorption coefficient K and scattering coefficient S of calculation coating film Y were each calculated. Similarly, from the relationship between spectral reflectance of calculation coating films W, R, and W-R obtained above, the absorption coefficient K and scattering coefficient S of calculation coating film R were each calculated. Similarly, the absorption coefficient K and scattering coefficient S of calculation coating B were calculated from the relationships with the spectral reflectances of calculation coatings W, B, and W-B obtained above. The coefficients k1 and k2 of the Sanderson correction formula were set to 0.04 and 0.57, respectively. The absorption coefficient K and scattering coefficient S calculated for each calculation coating are shown in Table 3.

[0064]

[0065] <Calculation Step> [[(E) First Calculation Step]] <Step of Predicting Tentative Mixture Composition Corresponding to Paint Properties> Example 1 Using the paint properties measured with a color meter SM-T, which is a tristimulus value direct reading color measuring device, as target values, a tentative mix corresponding to the paint properties of paint composition G was calculated by mathematical optimization using the absorption coefficient K and scattering coefficient S of calculation paint composition W, calculation paint composition K, and calculation paint composition G. The calculated tentative mix of paint composition G is shown in Table 4. Furthermore, for paint composition G, the color difference (ΔE ＊ ) are shown in Table 5.

[0066] [(F) Second Calculation Step] <(f1) Coefficient Ratio Calculation Step> Using Duncan's theoretical formula, K / S of paint composition G was calculated from the provisional formulation of paint composition G. <(f2) Second Spectral Reflectance Data Calculation Step> Using Kubelka-Munk's theory and the Sanderson correction formula, the spectral reflectance of paint composition G was calculated from K / S of paint composition G. The coefficients k1 and k2 of the Sanderson correction formula were the same as those described above. The calculation results are shown in Table 6. <(f3) Paint Properties and ΔE ＊ Calculation process: The color difference (ΔE ＊ For the coating composition G, the color difference (ΔE ＊ ), and the color difference (ΔE ＊ ) are shown in Table 7.

[0067] Example 2: Calculation was carried out in the same manner as in Example 1, except that the calculation coating film G to be calculated was changed to the calculation coating film Y. Example 3: Calculation was carried out in the same manner as in Example 1, except that the calculation coating film G to be calculated was changed to the calculation coating film R.

[0068]

[0069]

[0070]

[0071]

[0072] [[(G) Results]] As shown in Table 6, in all of the invention examples, the second spectral reflectance data of each primary colorant of the coating film color obtained using the provisional blend could be calculated. Also, as shown in Table 7, in all of the examples, ΔE ＊ In the example of the present invention, the tristimulus value direct reading method could be converted into spectrophotometric colorimetry.

Claims

1. A calculation method including a step of converting tristimulus value direct readings into spectrophotometric colorimetry, characterized in that the method is used for computer color matching using a computer.

2. A first acquisition step, which is a step of acquiring first spectral reflectance data of a first coating film obtained from a coating composition comprising primary colorants using a spectroscopic colorimeter, the first spectral reflectance data being data showing the relationship between wavelength and spectral reflectance; a second acquisition step, which is a step of acquiring color values ​​of each primary color colorant of a color of a second coating film obtained from a coating composition comprising primary color colorants using a tristimulus value direct reading colorimeter; and a first calculation step, which is a step of calculating a tentative blend of primary color colorants using the first spectral reflectance data acquired in the first acquisition step, such that the color values ​​measured using the spectroscopic colorimeter correspond to the color values ​​acquired in the second acquisition step, by a first calculation unit. a second calculation step of calculating, by a second calculation unit, second spectral reflectance data of each primary color colorant of a color of a coating film obtained using the temporary blend, using the first spectral reflectance data acquired in the first acquisition step, wherein the second spectral reflectance data is data showing a relationship between wavelength and spectral reflectance.

3. A method for calculating a spectral reflectance as described in claim 2, further comprising a coefficient calculation step of calculating an absorption coefficient K and a scattering coefficient S of each primary color colorant based on the first spectral reflectance data acquired in the first acquisition step, wherein in the first calculation step, a tentative blend of the primary color colorants is calculated using the absorption coefficient K and the scattering coefficient S calculated in the coefficient calculation step.

4. The method for calculating a spectral reflectance described in claim 3, wherein the second calculation step includes: a coefficient ratio calculation step of calculating a coefficient ratio K / S corresponding to the provisional blend based on the provisional blend calculated in the first calculation step and the absorption coefficient K and scattering coefficient S of each primary color colorant calculated in the coefficient calculation step; and a second spectral reflectance data calculation step of calculating the second spectral reflectance data from the calculated coefficient ratio K / S.

5. The method for calculating a spectral reflectance according to claim 2 or 3, wherein the first calculation step is performed using a mathematical optimization method or a brute force search method.

6. The method for calculating spectral reflectance according to claim 2 or 3, wherein the first coating film and the second coating film are the same coating film.

7. The method for calculating spectral reflectance according to claim 2 or 3, wherein the first coating film and the second coating film are different coating films, and the color difference ΔE between the first coating film and the second coating film is 2 or less.

8. The method for calculating spectral reflectance according to claim 2 or 3, wherein the number of types of the first coating film is 10 or more.

9. A method for producing a coating composition, which calculates a formulation suitable for obtaining a coating composition having desired coating properties by computer color matching using a computer, and obtains a coating composition using the calculated formulation, comprising: a first acquisition step, which is a step of acquiring first spectral reflectance data of a first coating film obtained from a coating composition consisting of primary color colorants using a spectral colorimeter, the first spectral reflectance data being data showing the relationship between wavelength and spectral reflectance; a second acquisition step, which is a step of acquiring color values ​​of each primary color colorant of a color of a second coating film obtained from a coating composition consisting of primary color colorants using a tristimulus value direct reading colorimeter; and a first calculation step, which is a first calculation unit, which uses the first spectral reflectance data acquired in the first acquisition step to calculate a tentative formulation of primary color colorants such that the color value measured using the spectral colorimeter corresponds to the color value acquired in the second acquisition step. a second calculation step in which a second calculation unit uses the first spectral reflectance data acquired in the first acquisition step to calculate second spectral reflectance data of each primary color colorant of the color of the coating film obtained using the temporary blend, the second spectral reflectance data being data indicating a relationship between wavelength and spectral reflectance; wherein the second spectral reflectance data calculated in the second calculation step is used in the computer color matching.

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